The invention relates to a support structure for vehicles, made from hollow steel sections, comprising a longitudinal member made from at least two hollow sections which are interconnected in parallel, wherein said hollow sections, in front of the support structure of the passenger compartment, bifurcate into a first hollow section supported by the lateral sill, and a second hollow section supported by other parts of the support structure.
Various designs of support structures of this type are known. U.S. Pat. No. 4,986,597 describes a design made from extruded aluminium sections comprising a longitudinal member which comprises two hollow sections, wherein the hollow sections reach both into the sill region and into the A-pillar of the support structure of the passenger compartment. A second structural member reaches from the A-pillar to the sill region so that overall, the longitudinal member, the A-pillar and the sill comprise a design featuring a double structural member. With such a design, a favourable force progression within a support structure is achieved without the need for separate gusset structures. There is a disadvantage in that there is a strong deflection to the A-pillar of the longitudinal forces experienced in the case of a crash. Moreover, aluminium extrusion technology cannot be used for steel materials in motor vehicle construction so that the findings cannot be transferred to steel constructions.
In another similar support structure (GB-A-529,631), but the hollow sections of which are composed of half-shell shaped profiles, a single longitudinal member branches in the direction of the passenger compartment into a first hollow section going over into the lateral sill of the passenger compartment and into a second hollow section supported on other parts of the support structure. Therefor starting from the branching point the longitudinal member is extending as a single hollow member in the direction of the bumper. For this reason in the case of a crash the longitudinal member will be deformed over its whole length up to the branching point. No means are provided for a stepwise reduction of the impact energy.
EP 0 749892 B1 describes a method for producing structural members of a support structure of vehicles, which structural members with the use of interior high-pressure metal forming technology comprise at least two hollow sections which in some regions are hollow sections that are interconnected in a positive-locking way.
Depending on the locally occurring load, the longitudinal member of this support structure comprises the hollow sections which are interconnected in a positive-locking way, as described above, or comprises a single hollow section. The structural members can be made from steel or light metal. Interior high-pressure metal forming technology implies material doubling at the connection surfaces of the hollow sections which are interconnected in a positive-locking way, so that the design is heavy if steel materials are used. The printed publication does not deal with the force progression in the support structure in the case of a crash.
DE 4208700 C2 describes a lateral sill which comprises two hollow sections of rectangular cross section, which sill, in the direction of the front of the vehicle, bifurcates into an engine compartment brace, positioned across the direction of travel, and into a bulkhead member which also extends across the direction of travel.
A lateral frame, arranged at the height of the engine compartment, is supported by the engine compartment brace and the bulkhead crossmember. In the case of a load in longitudinal direction of the vehicle as a result of a crash, said lateral frame ensures a lead-in of forces by deflecting the longitudinal forces to the lateral sill. Materials other than aluminium can be used. This design, too, is associated with the disadvantage of being heavy, in particular if steel materials are used, since among other things doubling of materials has to be accepted in the region of the lateral sill.
Finally, WO 92/11159 describes a rear panel of a vehicle body comprising two crossmembers, wherein each of the ends of the lower crossmember, which are bent in longitudinal direction of the vehicle, is connected to an impact absorber which forms the rear end of a longitudinal member. Apparently this is a longitudinal member which comprises a single hollow section.
Consequently, the crash energy introduced into the longitudinal member during impact from the rear is evenly absorbed along the entire length of the longitudinal member or transferred to the passenger compartment since no additional strengtheners of the design are provided to protect said passenger compartment.
It is thus the object of the present invention to provide a support structure for vehicles, of the type mentioned in the introduction, which support structure, with the use of high-strength steel materials with a light overall weight and a small number of components, provides improved crash behaviour.